The concordance correlation coefficient (CCC) [1]} is computed as the loss function for training the networks, as it is widely used in the retrieval of continuous emotions.
CCC score goes from 0 (chance level) to 1 (perfect) and is calculated according to the eq. REF , where \(x\)  correspond to the predicted value and \(y\)  the label. \(\mu _x\)  and \(\mu _y\)  are the means for the two variables and \(\sigma _x\)  and \(\sigma _y\)  are the corresponding variances. \(\rho \)  is the correlation coefficient between the two variables \(\sigma _x\)  and \(\sigma _y\)  therefore the covariance coefficient.
\(CCC = \frac{2\rho \sigma _x\sigma _y}{\sigma _x^2 + \sigma _y^2 + (\mu _x - \mu _y)^2}\) 
